Communication apparatus, method of controlling communication apparatus, and non-transitory computer-readable storage medium

ABSTRACT

A communication apparatus operable to communicate with a terminal station capable of operating in a Doze state and Awake state in an IEEE 802.11 ba, decides, based on a congestion degree in a channel for communicating with the terminal station in the Awake state, a waiting time for waiting for a response to a Wake-up frame for causing the terminal station to transit from the Doze state to the Awake state from when the Wake-up frame is transmitted, transmits the Wake-up frame while the terminal station is in the Doze state, and retransmits the Wake-up frame when the waiting time has elapsed after the Wake-up frame is transmitted without receiving the response from the terminal station.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a communication apparatus, a method ofcontrolling communication apparatus, and a non-transitorycomputer-readable storage medium.

Description of the Related Art

Currently, in IEEE 802.11ba, which is being standardized, it has beenproposed that a communication apparatus comprises a conventionalwireless LAN transmission/reception unit (hereinafter, a conventional RF(Radio Frequency) unit) and a WUR (Wake Up Radio) unit which operates totransmit and receive with lower power consumption (specification ofUS-2018-0255514). An STA (station) which is a wireless LAN terminalstation receives a WUR Beacon periodically transmitted from an AP(access point) while the STA is in a Doze state in which communicationis performed by the WUR unit. By receiving the WUR Beacon, the STA canmaintain synchronization with the AP without performing communication bya conventional RF unit.

When data to be transmitted from the AP to the STA is generated duringthe Doze state of the STA, the AP transmits a WUR Wake-up frame(hereinafter, referred to as a Wake-up frame) to the STA. The STA, afterreceiving the Wake-up frame, ends the Doze state and transits to anAwake state in which communication is performed by the conventional RFunit. Then, the conventional RF unit of the STA transmits a responsesignal to the AP with respect to the Wake-up frame, thereby notifyingthat the STA has transited to the Awake state. The AP, after receivingthe notification, recognizes that the STA has transited to the Awakestate and transmits data to the STA, and the conventional RF unit of theSTA can receive the data.

As described above, after the AP transmits a Wake-up frame in order tocause the STA to transit from the Doze state to the Awake state, the APwaits for the response signal with respect to the frame in order torecognize that the STA has transited to the Awake state. Here, aftertransmitting the Wake-up frame, the AP waits for reception of a responsesignal from the STA for a predetermined waiting time (Time Interval).The AP may retransmit the Wake-up frame if the AP is unable to receive aresponse signal from the STA within the predetermined waiting time. Areason why the AP cannot receive the response signal from the STA withinthe predetermined waiting time may be, for example, that the STA failedto receive the Wake-up frame. In contrast, even if the STA successfullyreceives the Wake-up frame, if a channel used to transmit the responsesignal is congested, it is possible that the AP will not be able toreceive the response signal from the STA within the predeterminedwaiting time. In this instance, although the STA has successfullyreceived the Wake-up frame, the AP must retransmit the Wake-up frame,and the STA and the AP consume unnecessary power and channel resources.

SUMMARY OF THE INVENTION

In view of the above problems, the present disclosure provides atechnique for preventing retransmission of unnecessary Wake-up frames byan AP.

According to one aspect of the present invention, there is provided acommunication apparatus operable to communicate with a terminal stationcapable of operating in a Doze state in which transmission or receptionof a frame other than a WUR (Wake-up Radio) frame in an IEEE 802.11 bastandard is not possible, and in an Awake state in which powerconsumption is higher than in the Doze state in the standard, whichcomprises: a decision unit configured to, based on a congestion degreein a channel for communicating with the terminal station in the Awakestate, decide a waiting time, which is a time period for waiting for aresponse to a Wake-up frame for causing the terminal station to transitfrom the Doze state to the Awake state from when the Wake-up frame istransmitted; a transmission unit configured to transmit the Wake-upframe while the terminal station is in the Doze state; and aretransmission unit configured to retransmit the Wake-up frame when thewaiting time has elapsed after the Wake-up frame is transmitted withoutreceiving the response from the terminal station.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments (with reference to theattached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a network configuration.

FIG. 2 shows an example of a hardware configuration of an AP.

FIG. 3 shows an example of a functional configuration of the AP.

FIG. 4 is a flow chart showing an example of a flow of processingexecuted by the AP for establishing a connection with an STA in the Dozestate, and performing Wake-up.

FIG. 5 is a flow chart showing Wake-up processing executed by the AP.

FIG. 6 shows an example of a conventional procedure for obtaining acongestion degree of an RF channel.

FIG. 7 shows an example of a Time Interval.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments will be described in detail with reference tothe attached drawings. Note, the following embodiments are not intendedto limit the scope of the claimed invention. Multiple features aredescribed in the embodiments, but limitation is not made an inventionthat requires all such features, and multiple such features may becombined as appropriate. Furthermore, in the attached drawings, the samereference numerals are given to the same or similar configurations, andredundant description thereof is omitted.

Network Configuration

FIG. 1 shows a configuration example of a network according to thepresent embodiment. FIG. 1 shows a network configuration that includesone station/terminal station (STA 101) and one access point (AP 102).The STA 101 and the AP 102 are wireless communication apparatuses thatsupport WUR conforming to the IEEE 802.11ba standard, and have aconventional RF (Radio Frequency) unit and a WUR unit (corresponding tothe conventional RF unit 211 and the WUR unit 212 shown in FIG. 2),respectively. As shown in FIG. 1, it is assumed that a range in which asignal transmitted by the conventional RF unit and the WUR unit of theAP 102 can be received is indicated by a communication range 103, and asignal transmitted by the AP 102 can be received by the STA 101. It isdesirable that the difference in the range in which a signal transmittedby the conventional RF unit and the WUR unit can be received is small,but there is no limitation to this. This network configuration is anexample, and the following discussion can be applied to, for example, anetwork including a large number of STAs and APs in a wide area, and tothe positional relationship of various communication apparatuses.

Configuration of AP

FIG. 2 shows a hardware configuration of the AP 102. As an example ofthe hardware configuration, the AP 102 includes a storage unit 201, acontrol unit 202, a function unit 203, an input unit 204, an output unit205, a communication unit 206, and an antenna 207.

The storage unit 201 is configured by one or more memories such as a ROMand a RAM, and stores various information such as programs forperforming various operations to be described later, communicationparameters for wireless communication, and the like. The storage unit201 stores information for managing the STA which is operating in theDoze state and connects to the AP 102. As the storage unit 201, astorage medium such as a flexible disk, a hard disk, an optical disk, amagneto-optical disk, a CD-ROM, CD-R, a magnetic tape, a nonvolatilememory card, a DVD, or the like may be used in addition to a memory suchas a ROM or a RAM.

The control unit 202 is configured by one or more processors such asCPUs and MPUs, and controls the entire AP 102 by executing a programstored in the storage unit 201. The control unit 202 may control theentire AP 102 in cooperation with a program stored in the storage unit201 and an OS (Operating System). In addition, the control unit 202 mayinclude a plurality of processors such as multi-cores, and the entire AP102 may be controlled by the plurality of processors. The control unit202 controls the function unit 203 to execute predetermined processingsuch as imaging, printing, and projection. The function unit 203 ishardware for the AP 102 to execute a predetermined process. For example,when the AP 102 is a camera, the function unit 203 is an imaging unitand performs an imaging process. For example, when the AP 102 is aprinter, the function unit 203 is a printing unit and performs aprinting process. For example, when the AP 102 is a projector, thefunction unit 203 is a projection unit and performs a projectionprocess. The data processed by the function unit 203 may be data storedin the storage unit 201, or data communicated from another communicationapparatus via a communication unit 206 described later.

The input unit 204 accepts various operations from the user. The outputunit 205 performs various outputs with respect to a user. Here, theoutput by the output unit 205 includes at least one of display on ascreen, sound output by a speaker, vibration output, and the like. Itshould be noted that both the input unit 204 and the output unit 205 maybe realized by one module as in a touch panel.

The communication unit 206 controls the conventional RF unit 211, theWUR unit 212, and the antenna 207 to transmit and receive wirelesssignals for wireless communication. The conventional RF unit 211controls wireless communication compliant with Wi-Fi or a standard ofthe IEEE 802.11 series (including the IEEE 802.11ba standard) andcontrols IP (Internet Protocol) communication. The conventional RF unit211 may communicate contents such as image data, document data, andvideo data with the STA 101 by using conventional RF channels. The WURunit 212 controls wireless communication compliant with IEEE 802.11ba(WUR function). Generally, since the AP 102 performs only transmissionprocessing in the WUR unit 212, the communication unit 206 can causeonly the transmission function of the WUR unit 212 to operate. The WURunit 212 transmits a WUR frame to an STA that is in the Doze state via aWUR channel. The WUR frame includes a WUR Beacon frame, a Wake-up frame,a WUR Discovery frame, or the like. A Wake-up frame is a frame forcausing the STA to transit from the Doze state to the Awake state. TheWUR Beacon frame and the WUR Discovery frame will be described later.For the antenna 207, although only one is shown in FIG. 2, configurationmay be taken to have two or more in order to perform MIMO(Multiple-Input Multiple-Output) communication.

The hardware configuration of the STA 101 is similar to that of FIG. 2,and as an example includes a storage unit 201, a control unit 202, afunction unit 203, an input unit 204, an output unit 205, acommunication unit 206, and an antenna 207. However, since the STA 101typically performs only reception processing in the WUR unit 212, thecommunication unit 206 can cause only the reception function of the WURunit 212 to operate. That is, the WUR unit 212 receives the WUR frame ina time period in which the STA 101 is in the Doze state. Further, theWUR unit 212, when having received a Wake-up frame, causes the Dozestate to end, and, via the communication unit 206 (or the control unit202), causes the conventional RF unit 211 to transit from the Doze stateto the Awake state (STA 101 enters the Awake state). The Doze state is apower saving state in which the function of transmitting and receivingsignals to and from the AP 102 using the conventional RF unit 211 isstopped. The Awake state is a state in which the conventional RF unit211 of the STA 101 can transmit and receive signals to and from theconventional RF unit 211 of the AP 102.

FIG. 3 is a diagram illustrating an example of a functionalconfiguration of the AP 102. The AP 102 includes, as an example of itsfunctional configuration, a connection processing unit 301, an analyzingunit 302, a WUR frame transmission control unit 303, a data frametransmission control unit 304, a congestion degree acquisition unit 305,a Time Interval decision unit 306, a timing control unit 307, and aretransmission count unit 308. The connection processing unit 301executes connection processing defined by a standard of the IEEE 802.11series via the conventional RF unit 211 of the communication unit 206.The analyzing unit 302 analyzes a signal received via the communicationunit 206. The WUR frame transmission control unit 303 controlstransmission of a WUR frame via the WUR unit 212 of the communicationunit 206. The data frame transmission control unit 304 controlstransmission of the data frame via the conventional RF unit 211 of thecommunication unit 206. The congestion degree acquisition unit 305acquires a congestion degree (congestion status) of the conventional RFchannel. After transmitting a Wake-up frame, the Time Interval decisionunit 306 decides a Time Interval which is a waiting time of a responsesignal for the frame. The timing control unit 307 performs a timemeasurement process from a predetermined timing and a process ofcomparing a measured time period with a predetermined time period. Theretransmission count unit 308 performs processing for counting thenumber of retransmissions of the Wake-up frame by the WUR unit 212, andcomparing the counted number of retransmissions with a predeterminednumber.

Processing Flow

Next, the flow of processing executed by the AP in the presentembodiment will be described with reference to FIGS. 4 and 5. Theprocessing shown in FIGS. 4 and 5 can be realized by the control unit202 executing a program stored in the storage unit 201. Note that theremay be a configuration while some or all of the processing shown inFIGS. 4 and 5 is implemented by hardware such as an ASIC. Here, ASIC isan abbreviation of Application Specific Integrated Circuit.

FIG. 4 is a flow chart showing an example of a flow of processing untilthe AP 102 establishes the connected state with the STA 101 in the Dozestate and executes Wake-up processing (processing for entering the Awakestate specified by a standard of the IEEE 802.11 series). The flow chartmay be started after activation of the AP 102 and prior to connection tothe STA 101. Further, it is assumed that this flow chart is started in astate where the WUR unit 212 of the AP 102 can communicate (a state inwhich WUR unit 212 is enabled). The IEEE 802.11ba standard defines anegotiation process for up until the start of WUR operation.

First, in step S400, the connection processing unit 301 of the AP 102executes connection processing specified by a standard of the IEEE802.11 series, and communicates WUR-specific information between the AP102 and the STA 101. Specifically, firstly, the connection processingunit 301 transmits a conventional Beacon frame or a Probe Response framethat include a WUR Capabilities Element indicating that the AP 102 is anAP that supports WUR. As a result, the STA 101, which is thecommunication partner apparatus, is notified that the AP 102 supportsWUR. The STA 101 transmits a Probe Request frame to the AP 102 and isnotified of the presence and the AP 102 and whether the AP 102 supportsWUR by receiving a Probe Response frame or receiving a Beacon frame thatis transmitted by the AP 102. The STA 101 then sends a AuthenticationRequest frame and an Association Request frame to the AP 102 to connectto the AP 102. The AP 102 establishes a connection by sending anAuthentication Response frame and an Association Response frames asrespective responses.

Here, the STA 101 includes, in the Authentication Request frame and theAssociation Request frame, information on an amount of time (TransitionDelay) required for the conventional RF unit 211 of the STA 101 totransit from the Doze state to the Awake state. In other words,Transition Delay is the amount of time required for the conventional RFunit 211 to be able to transit from the Doze state to the Awake stateand restart the transmission and reception of signals. Transition Delaymay be included in WUR Capabilities in a WUR Capabilities Element in theAuthentication Request frame and the Association Request frame.

Although a connection without encryption is described in thisembodiment, a connection with encryption defined by WEP, WPA1, WPA2,WPA3, or the like may be used. WEP is an abbreviation of WiredEquivalent Privacy and WPA is an abbreviation of Wi-Fi Protected Access.In addition, the AP 102 can share parameters required for WUR operationwith the STA 101 by including a WUR Operation Element in a particularmanagement frame. The parameters include a WUR Channel indicating WURtransmission channel information, a WUR Beacon Period indicatingtransmission intervals of WUR Beacon frames, and the like. A particularmanagement frame may refer to a Beacon frame, a Probe Response frame, anAssociation Response frame, or the like.

After a connection is established between the AP 102 and the STA 101,the STA 101 transmits an Action frame to the AP 102, to thereby requestthat the STA 101 start operation in the Doze state. The Action frame isdefined by IEEE 802.11ba as Category Code32. When 0 is set to a WURAction field in the Action frame, it means a WUR Mode Setup frame whichis a Doze state operation start request. However, when 1 is set to theWUR Action field, it means a WUR Mode Teardown frame which is a Dozestate operation end request. The WUR Mode Setup frame includes a WURMode Element which includes an Action Type field and a WUR Mode ResponseStatus Definition field. When the Action Type field indicating the typeof Doze state process is 0, it means an Enter WUR Mode Request, and whenit is 1, it means an Enter WUR Mode Response. When the WUR Mode ResponseStatus Definition field which indicates acceptance enabled/disabled fora receiving side is 0, it means Accept, and when it is 1 or 2, it meansDenied. Accept means that the AP 102 accepts the Doze state processingrequested by the STA 101, and Denied means that the processing isrejected. In the present embodiment, a frame having a WUR Mode Setupframe Action Type field of 0 is referred to as an Enter WUR Mode Requestframe. A WUR Mode Setup frame where the Action Type field is 1 isreferred to as an Enter WUR Mode Response frame.

The WUR Mode Element includes Starting Time Of The WUR Duty Cycleindicating the start time of a WUR Duty Cycle Period. The WUR ModeElement also includes On Duration and Duty Cycle Period. WUR Duty Cycledefines a WUR operation period, and a time period defined by On Durationin a time period for Duty Cycle Period indicates that the WUR STA is inthe Awake state. This ensures that the STA 101 (WUR STA) is in a statewhere it can receive a WUR frame from the AP 102 (WUR AP) during thistime period.

Subsequently, in step S401, the analyzing unit 302 of the AP 102monitors whether or not an Enter WUR Mode Request frame is received fromthe STA 101 by the conventional RF unit 211. If an Enter WUR ModeRequest frame has not been received (NO in step S401), reception isrepeatedly monitored. When an Enter WUR Mode Request frame is received(YES in step S401), the AP 102 WUR frame transmission control unit 303transmits an Enter WUR Mode Response frame with the WUR Mode ResponseStatus Definition field as 0.

Upon receiving the Enter WUR Mode Response frame, the STA 101 startsoperation in the Doze state, and causes the conventional RF unit 211 totransit to the Doze state. As a result, it is possible to suppress powerconsumed in communication with the AP 102 by the conventional RF unit.Subsequently, in step S402, the WUR frame transmission control unitperiodically transmits a WUR Beacon frame and a WUR Discovery frame.Configuration may be taken to transmit only one of the WUR Beacon frameand the WUR Discovery frame.

The WUR Beacon frame and the WUR Discovery frame will be describedlater. A WUR Beacon frame is defined in a WUR frame format, and istransmitted at the period of the WUR Beacon Period on a channel of WURChannel which is conveyed to the STA 101 in WUR Operation Element. A WURBeacon frame includes, for example, a Transmit ID for identifying the AP102 and a TD (Time Dependent) Control for synchronizing with the STA101. The STA 101 uses these pieces of information and Starting Time OfThe WUR Duty Cycle to synchronize the reception timings of WUR Beaconframes. Starting Time Of The WUR Duty Cycle is included in WUR ModeElement of a WUR Mode Setup frame.

A WUR Discovery frame is defined in a WUR frame format, and istransmitted according to information notified in a WUR Discovery Elementincluded in a conventional Beacon frame and a Probe Response frame. AWUR Discovery Frame is a WUR Frame used by a WUR STA to discover a WURAP. The parameters of WUR Discovery Frame are exchanged in this WURDiscovery Element via conventional RF units. More specifically, in achannel set in WUR Discovery channel, data is transmitted every periodthat is set as the WUR Discovery Period.

Next, in step S403, the AP 102 determines whether the STA 101 needs towake up (transition to the Awake state). The determination is performed,for example, when the control unit 202 determines that data desired tobe transmitted from the AP 102 to the STA 101 has occurred, or inresponse to an operation performed by a user via the input unit 204, orthe like. If the STA 101 needs to wake up, Wake-up processing isexecuted to transition the STA 101 which operates in the Doze state tothe Awake state (step S404). Wake-up processing will be described laterwith reference to FIG. 4.

During the processing of step S401 to step S404, the congestion degreeacquisition unit 305 of the AP 102 periodically (e.g., every one second)acquires the congestion degree (congestion state) of a conventional RFchannel in the background. FIG. 6 shows an example of a conventionalprocedure for obtaining a congestion degree of an RF channel. In FIG. 6,the horizontal axis represents time t. As an example of procedures foracquiring the congestion degree, the congestion degree acquisition unit305 calculates an evaluation value indicating the congestion degree fora predetermined time period T₀ 603. The evaluation value is calculatedas in Equation 1 for the predetermined time period T₀ 603 from the totalT_(CS) of the time period 601 determined to be busy when the AP 102performs a carrier sense process in the conventional RF channel and thetotal T_(TR) of the time period 602 occupied by the transmission andreception by the AP 102.

(T _(CS) +T _(TR))/T ₀   Equation 1

In Equation 1, both T_(CS) and T_(TR) are used, but either may be used.The congestion degree acquisition unit 305 may acquire the congestiondegree not while the STA 101 is in the Doze state (during the processingof step S401 to step S404), but during the Awake state prior to the STA101 transiting to the Doze state, or in a time between the Awake stateand the Doze state.

FIG. 5 is a flow chart showing an example flow of the Wake-up processing404 of the AP 102 in FIG. 4. First, in step S500, the Time Intervaldecision unit 306 of the AP 102 decides the Time Interval based on thecongestion degree (in the above example, an evaluation value thatindicates the congestion degree) of the conventional RF channel acquiredby the congestion degree acquisition unit 305. As described above, theTime Interval is a waiting time in which the AP 102 waits for a response(reception of response signal) from the STA after transmitting a Wake-upframe to the STA. When the WUR unit 212 of the STA 101 receives aWake-up frame, it starts the processing for Wake-up of the conventionalRF unit 211. At this time, if the conventional RF channel is congestedwhen the conventional RF unit 211 responds to the AP 102 by theconventional RF channel, there is a high possibility that a waiting timewill occur in transmitting the response signal. As a result, the AP 102cannot receive the response signal within the Time Interval, and the AP102 retransmits a Wake-up frame despite the Wake-up of the STA 101having succeeded. To prevent this, Time Interval decision unit 306 setsthe Time Interval to be longer when it is determined that theconventional RF channel is congested. The response signal transmittedfrom the STA 101 addressed to the AP 102 may be configured as a PS-Pollframe defined in the IEEE 802.11 series, for example.

FIG. 7 shows an example of a decided Time Interval. In the example ofFIG. 7, Time Interval decision unit 306 compares the evaluation value ofthe congestion degree of the conventional RF channel shown in Equation 1with a predetermined value (0.9), and depending on whether theevaluation value is greater than or equal to the predetermined value orless than the predetermined value, decides the Time Interval separately.For example, when the evaluation value of the congestion degree of theconventional RF channel shown in Equation 1 is 0.9 or more, the TimeInterval decision unit 306 determines that the congestion state of theconventional RF channel is “congestion”. Otherwise, the Time Intervaldecision unit 306 determines that the congestion status of theconventional RF channel is “normal”. When “congestion” is determined,Time Interval decision unit 306 decides the Time Interval as the timeperiod obtained by adding 1000 ms to Transition Delay 10. When “normal”is determined, Time Interval decision unit 306 decides the Time Intervalas the time period obtained by adding 50 ms to Transition Delay 10.

Next, in step S501, the WUR frame transmission control unit 303 of theAP 102 transmits a Wake-up frame to the STA 101 in the WUR channel. Atthe timing when Wake-up frame is transmitted, the timing control unit307 starts measuring a time period until the reception of the responsesignal. Thereafter, when the response signal is received from the STA101 (Yes in step S502), the data frame transmission control unit 304transmits data to the STA 101 in the conventional RF channel (stepS503). When the response signal is not received (No in step S502), thetiming control unit 307 determines whether the time period elapsedwaiting for the response signal (the time period measured by the timingcontrol unit 307) is less than the Time Interval decided in step S500(step S504). If the time period elapsed waiting for the response signalis less than the Time Interval (Yes in step S504), the processingreturns to step S502. When the time period elapsed waiting for theresponse signal is greater than or equal to Time Interval (time periodthat has elapsed is after the passage of Time Interval) (No in stepS504), the retransmission count unit 308 determines whether the presentnumber of retransmissions is less than a predetermined number (stepS505). If the present number of retransmissions is less than thepredetermined number (Yes in step S505), the process returns to stepS501, and the WUR frame transmission control unit 303 retransmits theWake-up frame. If the present number of retransmissions is greater thanor equal to the predetermined number (No in step S505), the WUR frametransmission control unit 303 does not further retransmit the Wake-upframe. The number of retransmissions may be decided prior to the firsttransmission of the Wake-up frame.

As described above, according to the present embodiment, it is possibleto prevent the AP from retransmitting unnecessary Wake-up frames andconsuming unnecessary power and WUR channel resources when the channelused in the Awake state is congested.

First Variation

In FIG. 6, a Time Interval corresponding to the congestion state isdecided in two steps, but the number of steps may be increased inaccordance with the evaluation value of the congestion state. Forexample, the Time Interval may be decided according to respectivecongestion conditions by setting “congestion” when the evaluation valueis 0.9 or more, “normal” when the evaluation value is 0.1 or more andless than 0.9, and “quiet” when the evaluation value is less than 0.1.Also, the value of the Time Interval is not limited to the values shownin FIG. 7. That is, it is sufficient if the Time Interval decision unit306 sets the Time Interval to a value greater than or equal toTransition Delay.

Second Variation

FIG. 4 described in the above embodiment discloses a flow chart for acase in which one WUR STA transitions to Doze operation. When there area plurality of STAs that perform communication based on the AP 102 andIEEE 802.11ba standard, the processing shown in FIG. 4 is executed forthe respective STAs in the same manner.

Other Embodiments

Embodiment(s) of the present invention can also be realized by acomputer of a system or apparatus that reads out and executes computerexecutable instructions (e.g., one or more programs) recorded on astorage medium (which may also be referred to more fully asanon-transitory computer-readable storage medium') to perform thefunctions of one or more of the above-described embodiment(s) and/orthat includes one or more circuits (e.g., application specificintegrated circuit (ASIC)) for performing the functions of one or moreof the above-described embodiment(s), and by a method performed by thecomputer of the system or apparatus by, for example, reading out andexecuting the computer executable instructions from the storage mediumto perform the functions of one or more of the above-describedembodiment(s) and/or controlling the one or more circuits to perform thefunctions of one or more of the above-described embodiment(s). Thecomputer may comprise one or more processors (e.g., central processingunit (CPU), micro processing unit (MPU)) and may include a network ofseparate computers or separate processors to read out and execute thecomputer executable instructions. The computer executable instructionsmay be provided to the computer, for example, from a network or thestorage medium. The storage medium may include, for example, one or moreof a hard disk, a random-access memory (RAM), a read only memory (ROM),a storage of distributed computing systems, an optical disk (such as acompact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™),a flash memory device, a memory card, and the like.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2019-084433, filed Apr. 25, 2019,which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. A communication apparatus operable to communicatewith a terminal station capable of operating in a Doze state in whichtransmission or reception of a frame other than a WUR (Wake-up Radio)frame in an IEEE 802.11 ba standard is not possible, and in an Awakestate in which power consumption is higher than in the Doze state in thestandard, the communication apparatus comprising: a decision unitconfigured to, based on a congestion degree in a channel forcommunicating with the terminal station in the Awake state, decide awaiting time, which is a time period for waiting for a response to aWake-up frame for causing the terminal station to transit from the Dozestate to the Awake state from when the Wake-up frame is transmitted; atransmission unit configured to transmit the Wake-up frame while theterminal station is in the Doze state; and a retransmission unitconfigured to retransmit the Wake-up frame when the waiting time haselapsed after the Wake-up frame is transmitted without receiving theresponse from the terminal station.
 2. The communication apparatusaccording to claim 1, wherein the decision unit decides the waiting timewhile the terminal station is operating in the Doze state.
 3. Thecommunication apparatus according to claim 1, wherein the decision unitdecides the waiting time while the terminal station is operating in theAwake state.
 4. The communication apparatus according to claim 1,wherein the decision unit decides the waiting time by adding apredetermined time period to a Transition Delay indicating a time periodrequired for the terminal station to switch from the Doze state to theAwake state.
 5. The communication apparatus according to claim 4,further comprising a calculating unit configured to calculate anevaluation value indicating a congestion degree for a predetermined timeperiod To in a channel for communicating with the terminal stationoperating in the Awake state, wherein the decision unit decides, as thewaiting time, a time period obtained by adding a predetermined firsttime period to the Transition Delay when the evaluation value is greaterthan or equal to a predetermined value, and, decides, as the waitingtime, a time period obtained by adding a predetermined second timeperiod lower than the predetermined first time period to the TransitionDelay when the evaluation value is less than the predetermined value. 6.The communication apparatus according to claim 5, wherein thecalculating unit, with respect to the fixed time period T₀, calculates,as the evaluation value, a total T_(CS) of a time period determined tobe busy when the communication apparatus performs a carrier senseprocess in a channel for communicating with the terminal stationoperating in the Awake state and/or a total T_(TR) of a time periodoccupied by the communication apparatus for transmission and receptionof signals in a channel for communicating with the terminal stationoperating in the Awake state.
 7. The communication apparatus accordingto claim 1, wherein the retransmission unit retransmits the Wake-upframe when the waiting time has elapsed after Wake-up frame istransmitted without receiving the response from the terminal station anda number of retransmissions of the Wake-up frame is less than apredetermined number.
 8. The communication apparatus according to claim1, wherein the transmission unit transmits a data frame on a channel forcommunicating with the terminal station operating in the Awake statewhen the response is received from the terminal station before thewaiting time elapses after the Wake-up frame is transmitted.
 9. A methodof controlling a communication apparatus that communicates with aterminal station capable of operating in a Doze state in whichtransmission or reception of a frame other than a WUR (Wake-up Radio)frame in an IEEE 802.11 ba standard is not possible, and in an Awakestate in which power consumption is higher than in the Doze state in thestandard, the method comprising: based on a congestion degree in achannel for communicating with the terminal station in the Awake state,deciding a waiting time, which is a time period for waiting for aresponse to a Wake-up frame for causing the terminal station to transitfrom the Doze state to the Awake state from when the Wake-up frame istransmitted; transmitting the Wake-up frame while the terminal stationis in the Doze state; and retransmitting the Wake-up frame when thewaiting time has elapsed after the Wake-up frame is transmitted withoutreceiving the response from the terminal station.
 10. A non-transitorycomputer-readable storage medium storing a computer program for causinga computer to execute a method of controlling a communication apparatus,wherein the communication apparatus is configured to communicate with aterminal station capable of operating in a Doze state in whichtransmission or reception a frame other than a WUR (Wake-up Radio) framein an IEEE 802.11 ba standard is not possible, and in a Awake state inwhich power consumption is higher than in the Doze state in thestandard, the method comprising: based on a congestion degree in achannel for communicating with the terminal station in the Awake state,deciding a waiting time, which is a time period for waiting for aresponse to a Wake-up frame for causing the terminal station to transitfrom the Doze state to the Awake state from when the Wake-up frame istransmitted; transmitting the Wake-up frame while the terminal stationis in the Doze state; and retransmitting the Wake-up frame when thewaiting time has elapsed after the Wake-up frame is transmitted withoutreceiving the response from the terminal station.